1. Field of the Invention
The present invention relates to a CMOS (complimentary metal oxide semiconductor) thin film transistor arrangement implemented by laminating a PMOS poly-silicon thin film transistor and an NMOS oxide thin film transistor, a method of manufacturing the same and an organic light emitting display device having the same.
2. Discussion of Related Art
A CMOS thin film transistor arrangement includes a PMOS thin film transistor and an NMOS thin film transistor, and can implement various circuits and a system that are difficult to be implemented by only PMOS thin film transistors or only NMOS thin film transistors. However, since the PMOS thin film transistor and the NMOS thin film transistor are required to be arranged on a single substrate in order to implement the CMOS thin film transistor arrangement, CMOS technology requires relatively many processes.
Moreover, the PMOS thin film transistor and the NMOS thin film transistor which make up the CMOS thin film transistor arrangement includes an active layer providing a channel region, a source region, and a drain region, and a gate electrode electrically insulated from the active layer by a gate insulating layer. The active layers of the thin film transistors are generally made out of a semiconductor layer such as amorphous silicon or poly-silicon.
When the active layer is made out of amorphous silicon, mobility is low so that it is difficult to implement a driving circuit driven at high speed. On the contrary, when the active layer is made out of poly-silicon, the mobility is high but threshold voltage is not uniform due to polycrystalline nature, so that a compensation circuit is required to compensate scattering of the threshold voltage. In addition, the mobility and yield are low when a poly-silicon active layer is used. Furthermore, the number of masks is higher for the poly-silicon active layer than for the amorphous silicon active layer due to a coplanar configuration, so that manufacturing costs are increased.
Therefore, in order to implement a CMOS thin film transistor arrangement, there is a need for simplify the manufacturing process while providing a satisfactory electrical performance.